Method and apparatus for using a rigid starter bar through a fixed bending unit

ABSTRACT

A continuous-casting machine using a rigid starter bar in which all the bending rolls are journaled on fixed axes. The pair of bending rolls which are below the tangent line have work-engaging faces offset horizontally from the work-engaging faces of the rolls above in the direction toward which the casting is bent, but the offset is insufficient to interfere with vertical movement of the starter bar between these rolls. Several rolls of the curved roll rack below the bending rolls are journaled in a switch section which can open to let the starter bar pass vertically or close to guide a casting.

United States Patent Quin Shen Yu, Forest Hills Borough, Pa.

Inventor:

Assignee: United States Steel Corporation,

Pittsburgh, Pa.

Filed: 0a. 1, 1971 Appl. No.: 185,644

US. Cl. 164/82; 164/274; 164/282 Int. Cl. B22D 11/08 Field of Search 164/82, 274, 282

References Cited UNITED STATES PATENTS 8/1967 Foldessy 164/274 [57] ABSTRACT A continuous-casting machine using a rigid starter bar in which all the bending rolls are joumaled on fixed axes. The pair of bending rolls which are below the tangent line have work-engaging faces offset horizontally from the work-engaging faces of the rolls above in the direction toward which the casting is bent, but the offset is insufficient to interfere with vertical movement of the starter bar between these rolls. Several rolls of the curved roll rack below the bending rolls are journaled in a switch section which can open to let the starter bar pass vertically or close to guide a casting.

6 Claims, 2 Drawing Figures U.S. Patent Oct. 14, 1975 Sheet 1 of2 3,911,995

Tangent L ine U.S.' Patent Oct.14, 1975 Sheet2of2 3,911,995

METHOD AND APPARATUS FOR USING A RIGID STARTER BAR THROUGH A FIXED BENDING UNIT This invention relates to a continuous-casting machine which uses a rigid starter bar and has an improved arrangement of bending rolls, and to an improved method of handling a rigid starter bar.

In a conventional continuous-casting operation, liquid metal is poured through an open-ended watercooled vertically oscillating mold. A casting, which at this stage has only a relatively thin solidified skin and a liquid core, emerges continuously from the lower end of the mold. Before a casting operation begins, a starter bar is inserted in the mold to close the lower end. The starter bar, which may be either rigid or flexible, is withdrawn from the mold ahead of the casting. At some point below the mold the starter bar is disconnected from the leading end of the casting and stored until needed to start the next cast.

In machines which use a rigid starter bar, the starter bar and casting travel through a straight vertical guideroll rack immediately below the mold and through an assembly of power-drive pinch rolls beneath the guideroll rack. The starter bar is disconnected below the pinch-roll assembly and drops into a suitable receiver, such as a basket hoist. Following the pinch rolls, the casting travels through a set of bending rolls, which impart a curvature to the casting. Thereafter the curved casting travels through a curved roll rack, which changes its direction of travel from vertical to horizontal, and ultimately through a straightener. All the while intense water sprays are applied to the casting surface to promote solidification. After the casting is solidified throughout, it is severed to appropriate lengths.

To accommodate a rigid starter bar, several rolls of the curved roll rack are journaled in switch sections which open to allow the starter bar to pass vertically. Thereafter the switch sections are closed to guide the casting into its curved path. Heretofore at least one of the bending rolls has been journaled in a switch section, along with the rolls of the curved roll rack. There have been two switch sections on opposite sides of the casting. Reference can be made to Foldessy U.S. Pat. No. 3,338,297 for an exemplary showing. This arrangement has disadvantages that bending rolls, which sustain large forces required to bend the casting, must be shifted, and also that it is difficult to coordinate movement of two switch sections so that both close at exactly the right time to pick up the leading end of the casting after the starter bar is disconnected.

An object of my invention is to provide, in a continuous-casting machine using a rigid starter bar, an improved arrangement of bending rolls in which I overcome the foregoing disadvantages, that is, I avoid journaling any of the bending rolls in a switch section and I use only a single switch section.

A further object is to provide an improved arrangement of bending rolls which enables a rigid starter bar to pass vertically, yet avoids need for shifting any of the bending rolls, and necessitates opening and closing only a single switch section.

A further object is to provide an improved method of handling a rigid starter bar in which I move the bar through a set of bending rolls without shifting any of them, and open and close only a single switch section below and independently of the bending rolls.

A further object is to provide an improved mechanism for opening and closing a switch section in a continuous-casting machine, which mechanism embodies a toggle linkage affording positive support for the switch section when closed.

In the drawing:

FIG. 1 is a partly diagrammatic side elevational view of a continuous-casting machine in which the bending rolls are arranged in accordance with my invention, the switch section being shown in its closed position; and

FIG. 2 is a similar view with the switch section in its open position.

The machine illustrated includes from top to bottom an open-ended water-cooled vertically oscillating mold 10, a straight vertical guide-roll rack 12, an assembly of power-driven pinch rolls 13, a set of bending rolls 14, and a curved roll rack 15. The rolls, other than the pinch rolls, can be idlers or various rolls can be driven, as known in the art. The machine has a rigid starter bar 16, which is disconnected from a casting after the leading end of the casting passes the pinch rolls, also as known in the art. Reference can be made to Gallucci U.S. Pat. No. 3,448,789 for an exemplary showing of a suitable starter bar and disconnect mechanism. A basket hoist 17 receives the disconnected starter bar. Except for the bending rolls and adjacent portion of the curved roll rack, the foregoing parts can be of conventional construction; hence I have not shown or described them in detail. I have not shown the water sprays, the lower portion of the curved roll rack nor the parts beyond, since they are not involved in my invention.

FIG. 1 shows a casting C extending through the guide-roll rack 12, pinch roll assembly 13 and bending rolls 14 into the curved roll rack 15. The set of bending rolls includes two clusters 14a and 14b, which contact the convex face of the casting C, and two clusters 14c and 14d, which contact the concave face. The upper roll 20 of cluster 14d is the fulcrum roll, which defines the tangent line where the casting first acquires a curvature. In accordance with my invention, all the bending rolls are journaled on fixed axes. The workengaging faces of the fulcrum roll 20 and of the opposite roll on the convex side and of the bending rolls thereabove in clusters 14a and lie in the same vertical planes as the work-engaging faces of the guide rolls l2 and pinch rolls 13. The work-engaging faces of the lower rolls 21 and 22 of clusters 14b and 14d are offset horizontally from these planes about 3/16 to 7/32 inch in the direction toward which the casting C curves. This relatively small offset is sufficient to bend the casting on a radius of curvature of about 31 to 33 feet.

This curved roll rack 15 has only a single switch section 23. This section includes a frame 25 pivoted at 26 to the supporting structure 27 of the machine. A plurality of rolls 28 are journaled in frame 25 for contacting the convex face of the casting. When the switch section 23 is closed, as shown in FIG. 1, the work-engaging faces of rolls 28 lie along an arc which is a continuation of the arc defined by the rolls below. The uppermost roll 28 lies just below the lower roll 21 of the bending roll cluster 14b. For opening and closing the switch sec tion, I connect a toggle linkage 29 between the supporting structure 27 and frame 25. I connect a fluidpressure cylinder and piston 30 between the supporting structure and the toggle joint. When the piston rod is extended, the toggle linkage affords positive support for the switch section.

FIG. 2 shows the relation of the parts when the switch section 23 is open. There is a slight clearance between the starter bar 16 and the rolls of the guide-roll rack 12. The pinch rolls 13 are spring loaded, known in the art, whereby they grip the starter bar well as the casting C, which is somewhat thicker than the starter bar. Reference can be made to Gallucci US. Pat. No. 3,550,676 for an exemplary showing of suitable springloaded pinch rolls. The offset of roll 21 toward the starter bar is sufficiently small that the starter bar can move past vertically without interference. The switch section 23 operates independently of the bending rolls 14.

From the foregoing description, it is seen that my invention affords a simple bending roll arrangement for accommodating a rigid starter bar, yet keeping all bending rolls journaled on fixed axes. The invention also affords a method of handling the starter bar without shifting any of the bending rolls. In installations where space is at a premium, a rigid starter bar is advantageous over a flexible bar, since a flexible bar necessitates a long run-out conveyor. My invention facilitates use of a rigid bar in such installations, since it overcomes other problems encountered with a rigid bar.

I claim:

1. In a continuous-casting machine, which includes a mold, a guide-roll rack below said mold, an assembly of power-driven pinch rolls below said guide-roll rack, a set of bending rolls below said pinch rolls, a curved roll rack below said bending rolls, and a rigid starter bar adapted to be disconnected from a casting after the leading end of the casting passes said pinch rolls, said bending rolls including a fulcrum roll which defines a tangent line where the casting first acquires a curvature and other rolls which contact the convex and concave faces of the casting both above and below said tangent line, the improvement comprising a switch section in which several rolls of the curved roll rack are journaled, said switch section being shiftable to an open position to allow said starter bar to pass vertically and to a closed position to guide the casting into the rolls below, said bending rolls below said tangent line having work-engaging faces offset horizontally from the workengaging faces of the rolls above in the direction toward which the casting curves, but being journaled on fixed axes.

2. A machine as defined in claim 1 in which the distance of offset is about 3/16 to 7/32 inch, which bends the casting on a radius of about 31 to 33 feet, but is insufficient to interfere with vertical movement of said starter bar.

3. A machine as defined in claim 1 in which there is only a single switch section and the only rolls journaled therein are located on the convex side of the casting.

4. A machine as defined in claim 3 in which said switch section includes a frame in which the rolls are journaled, means pivotally supporting said frame, and a toggle linkage connected to said frame for shifting the section between its open and closed positions, said linkage affording positive support for said section in its closed position.

5. A method of handling a rigid starter bar in a continuous-casting machine which includes a set of bending rolls, said method comprising withdrawing the starter bar ahead of a casting in a vertical direction, moving the starter bar past the bending rolls without shifting the bending rolls, and bending the casting to a curvature after the starter bar is disconnected from the leading end thereof.

6. A method as defined in claim 5 in which a switch section below the bending rolls is opened to allow the starter bar to pass vertically and closed to guide the casting independently of the bending rolls. 

1. In a continuous-casting machine, which includes a mold, a guide-roll rack below said mold, an assembly of power-driven pinch rolls below said guide-roll rack, a set of bending rolls below said pinch rolls, a curved roll rack below said bending rolls, and a rigid starter bar adapted to be disconnected from a casting after the leading end of the casting passes said pinch rolls, said bending rolls including a fulcrum roll which defines a tangent line where the casting first acquires a curvature and other rolls which contact the convex and concave faces of the casting both above and below said tangent line, the improvement comprising a switch section in which several rolls of the curved roll rack are journaled, said switch section being shiftable to an open position to allow said starter bar to pass vertically and to a closed position to guide the casting into the rolls below, said bending rolls below said tangent line having work-engaging faces offset horizontally from the work-engaging faces of the rolls above in the direction toward which the casting curves, but being journaled on fixed axes.
 2. A machine as defined in claim 1 in which the distance of offset is about 3/16 to 7/32 inch, which bends the casting on a radius of about 31 to 33 feet, but is insufficient to interfere with vertical movement of said starter bar.
 3. A machine as defined in claim 1 in which there is only a single switch section and the only rolls journaled therein are located on the convex side of the casting.
 4. A machine as defined in claim 3 in which said switch section includes a frame in which the rolls are journaled, means pivotally supporting said frame, and a toggle linkage connected to said frame for shifting the section between its open and closed positions, said linkage affording positive support for said section in its closed position.
 5. A method of handling a rigid starter bar in a continuous-casting machine which includes a set of bending rolls, said method comprising withdrawing the starter bar ahead of a casting in a vertical direction, moving the starter bar past the bending rolls without shifting the bending rolls, and bending the casting to a curvature after the starter bar is disconnected from the leading end thereof.
 6. A method as defined in claim 5 in which a switch section below the bending rolls is opened to allow the starter bar to pass vertically and closed to guide the casting independently of the bending rolls. 